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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id h185sm2531667qkf.85.2020.07.21.07.15.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jul 2020 07:15:45 -0700 (PDT) Date: Tue, 21 Jul 2020 10:15:39 -0400 From: Qian Cai To: Michal Hocko Cc: linux-mm@kvack.org, LKML , Andrew Morton , Linus Torvalds , Tim Chen Subject: Re: [RFC PATCH] mm: silence soft lockups from unlock_page Message-ID: <20200721141539.GA3696@lca.pw> References: <20200721112529.GJ4061@dhcp22.suse.cz> <664A07B6-DBCD-4520-84F1-241A4E7A339F@lca.pw> <20200721121752.GK4061@dhcp22.suse.cz> <20200721132343.GA4261@lca.pw> <20200721133835.GL4061@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200721133835.GL4061@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 21, 2020 at 03:38:35PM +0200, Michal Hocko wrote: > On Tue 21-07-20 09:23:44, Qian Cai wrote: > > On Tue, Jul 21, 2020 at 02:17:52PM +0200, Michal Hocko wrote: > > > On Tue 21-07-20 07:44:07, Qian Cai wrote: > > > > > > > > > > > > > On Jul 21, 2020, at 7:25 AM, Michal Hocko wrote: > > > > > > > > > > Are these really important? I believe I can dig that out from the bug > > > > > report but I didn't really consider that important enough. > > > > > > > > Please dig them out. We have also been running those things on > > > > “large” powerpc as well and never saw such soft-lockups. Those > > > > details may give us some clues about the actual problem. > > > > > > I strongly suspect this is not really relevant but just FYI this is > > > 16Node, 11.9TB with 1536CPUs system. > > > > Okay, we are now talking about the HPC special case. Just brain-storming some > > ideas here. > > > > > > 1) What about increase the soft-lockup threshold early at boot and restore > > afterwards? As far as I can tell, those soft-lockups are just a few bursts of > > things and then cure itself after the booting. > > Is this really better option than silencing soft lockup from the code > itself? What if the same access pattern happens later on? It is better because it does not require a code change? Did your customers see the similar soft-lockups after booting was done?